In U.S. Pat. Nos. 4,543,990 and 4,589,690 (Meuleman) valves are disclosed which are intended for use in gated irrigation pipe. These patents describe the general background of irrigation using gated pipe which will not be repeated herein.
The present invention involves an improvement to valves of the type shown in those patents. Those valves include a valve housing which has a tubular passage and an attachment arrangement for connecting the passage to an opening in an irrigation pipe which has a significantly larger diameter than the passage. An inlet opening permits water to flow from the pipe into the passage. The passage receives a tubular valve member which slides into the passage and can be rotated therein. The valve member has an open bottom end and a flow opening in its cylindrical wall which can be aligned with the inlet opening in the tubular passage to permit water to flow from the pipe into the interior of the valve member and out of its open bottom. The flow is simply a gravity flow, the rate of which is determined, in part, by the level and pressure of the water in the irrigation pipe.
The flow is also controlled by the rotational position of the valve member to alter the degree of overlap of the inlet opening and the flow opening. As the valve member is rotated away from the fully-aligned position, the opening overlap is decreased, decreasing the total amount of water which can pass through the valve. While this control is necessary and desirable to optimize the use of irrigation water, it has been found that under certain pressure conditions, the water tends to flow in a circular pattern through a partly open valve, resulting in a fan-shaped discharge from the bottom of the valve member. This fan-shaped discharge pattern has a highly undesirable erosion effect when it strikes the soil below the valve. The effect is particularly noticeable when the valve is made rather short, even though it is desirable to make the valve short for cost and other reasons.
It has also been found with the valves disclosed in the above-mentioned patents that, under field conditions, dirt tends to accumulate between the tubular passage and the valve member, requiring that the valve be periodically disassembled and cleaned, an undesirable maintenance problem.